This invention relates, in general, to semiconductor devices, and more particularly to a semiconductor die having rounded or tapered edges and corners.
A semiconductor device in which this invention will typically be used includes a silicon semiconductor die having metal interconnect lines which are covered by passivation glass. The die is mounted on the flag of a leadframe and the die and flag are then encapsulated in plastic at a high temperature. The expansion coefficient of the plastic encapsulant is much larger than that of the silicon die and, therefore, the plastic encapsulant cannot fully contract during cooling. In large packages, deleterious results of this thermal expansion mismatch are especially evident during temperature cycling tests where the temperature extremes often range between -65 and 150 degrees centigrade.
When the plastic encapsulant contracts, large magnitudes of stress act on the silicon semiconductor die. The stress is highest on the edges and corners of the die. The stress causes the plastic encapsulation to crack adjacent to the corner of the semiconductor die which allows for relative motion between the plastic encapsulant and the semiconductor die. This motion causes the passivation glass of the semiconductor die to crack and break, further causing delamination. This delamination commonly travels through the metal interconnect lines and results in a semiconductor device having a decreased lifetime. Therefore, it would be advantageous to provide a semiconductor device having a higher resistance to stress failure caused by the difference of expansion between the plastic encapsulant and the silicon die.